XDH and COVID-19: Hence, a disbalance of endothelial-derived oxidative and anti-oxidative factors in COVID-19 patients can be expected, and the extent of this disbalance might correlate with disease severity.<h4>Methods</h4>We measured xanthine oxidase (XO), superoxide dismutase (SOD), catalase (CAT), and ischemia modified albumin (IMA) in serum samples of 166 COVID-19 patients and 238 controls.